TAPPI TIP 0304-53
Tests for corrugator roll wear
|Publication Date:||1 January 2015|
Singlefacer corrugator rolls are very important components in the corrugating process. They produce the fluted medium which is the foundation on which the quality of corrugated board is based. If the condition of the corrugator rolls is allowed to deteriorate, board quality and corrugator productivity will deteriorate with it.
Corrugator rolls are hollow steel cylinders, with gearlike teeth (or flutes) machined onto the surface. The entire surface is overlaid with a coating - often chrome or tungsten carbide - which protects the underlying steel flutes from wear. During the running life of a corrugator roll, wear caused by friction from the corrugating medium gradually wears away the roll coating, thus exposing the machined steel teeth underneath to wear. If the base metal is allowed to wear without recovering it with a fresh coating, a noticeable drop in flute height (caliper) will occur, and high-lows (a condition whereby flutes are not uniform height exiting the corrugators rolls) will become more pronounced. The corrugator roll will have to be recut, rebuilt to original specifications, or even scrapped.
A simple test, called the copper sulfate test, can be run to determine the condition of corrugator rolls.
NOTE 1: The copper sulfate test works well to expose the wear patterns on chrome-plated corrugator rolls. A commercial product called Insta-Blak can only be used on tungsten carbide-coated rolls, as well as rolls with a stainless steel substrate. It is more effective on such substrates and can be used similarly to the copper sulfate solution. It will turn exposed steel/stainless steel black in color.